1. Touch, Taste, Smell

2. Chemoreceptors Pain receptors Thermoreceptors Mechanoreceptors
Smell and taste
Pain receptors
touch
Thermoreceptors
Taste and touch
Mechanoreceptors
Hearing (proprioreceptors)

3. Dermal Structures Receptors Location Function Bare nerve endings
Meissner’s corpuscles
Pacinian corpuscles
Merkel’s Disks
Ruffini’s corpuscles

4. Pain Receptors Provide protection Do not adapt rapidly Stimulated by
Changes in temperature
Mechanical force

5. Smell Olfactory organ Appear as the yellowish mass
They are covered by a pinkish mucous membrane
Nasal cavity, superior nasal conchae, nasal septum
Contain the olfactory receptor cells (400 receptors in human)

6. How we smell Olfactory receptors
bipolar neurons surrounded by columnar epithelial cells
Chemoreceptor
Gas partially dissolves
Knobs at distal end of dendrites covered with hair-like cilia
Generates nerve impulse
(travel along axon through openings of cribriform plates of ethmoid bone)

7. Sensory impulses are analyzed within olfactory bulbs.
fibers synapse with neurons located in the enlargement of the olfactory bulbs:
Structures that lie on either side of the crista galli of the ethmoid bone.
Sensory impulses are analyzed within olfactory bulbs.

9. Unique characteristics
Undergo sensory adaptation rather rapidly.
intensity of an odor drops 50% within a second following the stimulation.
Within a minute may become insensitive to odor.
Only nerve cells in direct contact with the outside environment.
Subject to damage
Only damaged neurons that are regularly replaced.

10. Taste Saliva (must dissolve)
Combination of chemicals binding to specific receptors on taste hair surfaces
Binding results in depolarization
Degree of change is directly proportional to concentration of tasted substance

11. Taste Burning Sensation 5 primary tastes
Flavors results of one (or combination of) flavor(s) on tongue
Sweet (tip)
Sour (margins)
Salty (everywhere)
Bitter (back)
Umami (unknown)
Different factors may influence taste
Temperature
Smell
Texture
Burning Sensation
Capaisin-irritant

12. Taste Receptors Gustatory/ taste cells spherical Taste pore
Modified epithelial cells
Function as receptors in the taste buds.
Each of our 10,000 taste buds houses taste cells.
spherical
Taste pore
Located on the free surface, an opening where projection (microviilli) protrude

13. Chemicals dissolve in saliva
Masticate food
Chemicals dissolve in saliva
Network of nerve fibers are interwoven and wrapped around taste cells.
Ends of the fibers closely contact receptor cell membranes.
Stimulated receptor cell triggers an impulse on a nearby nerve fiber.
Facial
Glossopharyngeal
vagus nerves
Then travels to the brain.

14. Impulses
Medulla oblongata  up thalamus  to gustatory cortex (parietal lobes for interpretation)

16. Functions for ~ 3 days then replaced
Exposed to external environment but not as high turnover as nose